Cyclic voltammetric stripping (CVS) analyzer with a rotating disk electrode (RDE) is an established method to evaluate the composition concentration in plating baths. The CVS applies a reversible potential sweep to firstly deposit metal onto the surface of the rotating disk electrode, and then strips the metal back into solution. These cycles of ramps in potential may be repeated as many times as desired. The current at the working electrode is plotted versus the applied voltage to give a cyclic voltammogram trace.
The rotating disk electrode rotates during experiments and induces a flux of analyte to the electrode. The electrode includes a conductive disk embedded in an inert non-conductive polymer or resin that can be attached to an electric motor providing fine control of the electrode's rotation rate. The disk is mostly made of a noble metal or glassy carbon. As the disk turns, some of the solution is dragged by the spinning disk and the resulting centrifugal force flings the solution away from the center of the electrode. Solution flows up, perpendicular to the electrode, from the bulk to replace the boundary layer as shown in FIG. 1A. It results a laminar flow of solution towards and across the electrode. The rate of the solution flow can be controlled by the electrode's angular velocity and modeled mathematically. This flow can quickly achieve conditions in which the steady-state current is controlled by the solution flow rather than diffusion.
Nevertheless, as the electrode has to be rotated during analysis, a simple electrical wire, connecting the conductive disk and CVS analyzer for transmitting current, can not be used since the electrical wire is twisted under rotation. Thus, special design of the electrical contact has to be used. To solve this problem, the electrical contact is designed as shown in FIG. 1B. A conventional RDE 100 comprises a brush contact 101, a lower bearing assembly 102, a motor coupling 103, an attachment structure 104, and an electrode shaft 105. The brush contact 101 is a spring-loaded silver-carbon brush providing electrical contact with the rotating electrode shaft 105. The lower bearing assembly 102 can stabilize the rotating electrode shaft 105 at the point where the electrode shaft 105 exits a motor unit. The motor coupling 103 is used to attach the electrode shaft 105 to the motor. The attachment structure 104 is used to attach the electrode shaft 105 to the motor and comprises hex screws located on either side of the motor coupling 103 and being tightened to hold the electrode shaft 105 inside the motor coupling 103. The top end of the rotating electrode shaft 105 is mounted in the motor coupling 104 and the active electrode surface is located at the bottom end of the electrode shaft 105. However, the drawbacks of such electrical contact using the brush contact and the electrically conductive electrode shaft are expensive due to precision rotating control parts required, and short working life due to rotation wearing at the rotating electric contact. Furthermore, it is also difficult to fabricate the electrical contact since vibration or drifting of the electrode pole frequently appears.
Therefore, there is an unmet need to provide an electrode for electrochemical bath analysis having simplified electrical contact design.